Frequency control for ultra high frequency devices



a t., l May M? 344; R. M. SMITH 2,349,011

FREQUENCY CONTROL FOR ULTRA HIGH FREQUENCY DEVICES 'Filed July 31, 1941 2 sheets-sheet 1 vaL Maf 4 4 Y Gttorneg l5, E'. R. M. SMITH 2,349,0l1

FREQUENCY CONTROL FCR ULTRA HIGH FREQUENCY DEvCEs `Filed. July 31, 1941 2 Sheets-Sheet 2 1 l 111|' v ['11, l l l l Patented May i6, v1944 FREQUENCYCONTBOL FOB ULTRA HIGH FREQUENUY DEVIGES negers M. smith, Ashland Terrace, N. J., einer to Radio Corporation of America, a corporation o! Delaware application .my 31,1941, serial No. 404,356l

This invention relates to improvements in the frequency controls forultra.` high frequency` de- I 9 claims. wieso- 27) .vices and particularly to an ultra high frequency scondarily emissive thermionic tube in ,which lthe frequency characteristic is controlled by adjusting the length of the electron paths and hence,

the electron transit time.

In conventional therinlonic tubes operating at frequencies of .the order -of 100 megacycles per second and downwardly throughout the lowerfrequencies' the transit time of the electrons passing from cathode to anode has al negligible elect on the operating frequency. As the tubes are operated at frequencies of the order of 500 megacycles per second the 'eects of electron transit time become appreciable, and limiting factor. l y While transit time acts as a limiting factor in conventional tubes operated at the lower frequencies. the electron ight time in a tube operated at the higher frequencies may be used to control the frequency, to control regeneration or degeneration, to 'compensate forcircuit varias tions, and to provide multiple band operation. Thusit is one of the objects of the instant in vention to provide means for utilizing the electron transit time to control 'the operation of an ultra high frequency device. An additional object is to provide means for controlling the electron transit time in a secondary emissive device thereby to control its operation. Another object is to provide improved means in'an oscillatory circuit including a secondary emissive device for controlling frequency, regeneration, circuit variations and frequency response characteristic o f the circuit.

The invention will be described by referring to the. accompanying drawings in which Fig. 1 is a schematicdiagram ofone embodiment of the invention; Figs. 2, 3 and 4 are graphs illustrating modes of operation; Fig. 5 is a schematic diagram of a modication; and Figs. 6 and 7 are schematic diagrams of push pull circuits embodying the invention. Similar reference charactersv indicate similar elementsin the drawings.

Referring to'Fig. 1, within'an evacuated envelope I are arranged: a heater 3, a cathode 5, a control grid 1, a screen grid 9, a pair of deiectin 'fact act as a frequency respectively, tc the 'adjustable terminals cf'potentiometers 2l, 23. The potentiometers are con' nected, respectively, through resistors 25, 21, or other Asuitable inputs for modulation voltages,l to ground. The modulation voltages will be hereinafter described. The secondary emissive electrode is connected either directly' or through animpedance 29 toa positive terminal of the B voltage so'rce. The anode I1 Vis connected through an oscillatory circuit 3| to 'a positive 'terminal of Ithe B voltage source. The oscillatory circuitmay be coupled/directly or indirectly to an output or` load circuit.

In the normal operation-of the device electrons released from the cathode 5.travel along curvi linear paths 33 to the secondary emissive electrode I5 von which the lectrons impinge. The impinging electrons release secondary electrons, which travel'to the anode Il and hence through the oscillatory circuit 3l where resonance establishes oscillatorycurrents. It should be understood that the amplitude of theelectronic currentsvaries as a function of the frequency of the applied signal potentials.

It has been discovered that when the' oscillatory circuits have been tuned tb a. period corresponding to 500 megacycles, by way of example, and f the electron transit require'sa period of the same A order, variations in the electron transit time have a reactive influence on the circuit.,v The reactive influence may be readily controlled by changing the potentials applied to either or -both deflecting electrodes II, I3. Thus by makngelectrode Il more positive, the electrons take the longer path percent. In these ranges calculations showed that the electron transit time approached the period' of the operating frequency.

ing electrodes Il, I3, a secondary emissive electrcde I5, and an' anode II. The control grid l is.

connected through an oscillatory circuit IS to ground. The oscillatory circuit I9 is coupled or connected to a signal input source. The screen grid is connected to a B-voltage source which is not shown.

The deflecting electrodes l'l, I3 are connected,

-The described method of operation may be used i to change the response frequency of the circuit by adjusting the potentiometers 2|, 23 without Achanging the oscillatory circuits. Furthermore; as shown' i'n Fig. 2, a modulation voltagel of a square wave form 39 may be applied to the resistors 25 and/or 2l so that alternate frequency responses are obtained.

'matched or'transformed. if transformation. is

desired.4 A 'blucking cmcltor'l is included in The one'peak Il corresponds to modulation voltage a and the'other peak I3 corresponds to modulation voltage b. It desired. the circuits I9 and 3| may be' adjusted so that degeneration occurs at the higher frequency and regeneration at Q the lowerfrequency. as the'modulation voltages `a and b are appliedfas shown by the dash'lline lil.

. By applying, a sawtooth modulation wave 41 as shown in Fig. 8, they reSDOnse curve may be marier to move through a range of frequencies lo as represented by a series of response curves I9. Ii' the sawtooth frequency is very high, the

` resultant response will have a hemdA pass characteristlc represented -by the dash line Qi.

Regeneration may be controlled by varying the 15 impedance 29 to broaden or sharpen the frequency response cf the device as shown bythe curves 53:55, respectively. oi Fig- 4.

One suitable circuit forv controlling regeneration is shown in ris. s; 'rnc ames input cir- 20 cuit is represented as a quarter wave concentric line 51 to which the input signal is applied at a suitable impedance point I9. The tuned output circuit isslso represented as a quarter wave concentric line il to .which an output lead B3 25.

may be connected to the line 8i at an appropriate impedance point.

The impedance or regeneration control circuit consistsof a half wave concentric line 65 to which the emissive electrode IB-is 'connected 30 at a chosen point 81 on the inner conductor. 'I'he leil'ectof moving the connectionas a function of the distance d from the grounded tertion may be regulated bythe point I'l at which the secondaryemissive electrode is connected.-

4 The lengthl l is the factor determining the 40 amount of. impedance Z which is included in the emission electrode circuit. It has been found f that the frequency o! the circuit may also be controlled most effectively by varying' the impedance Z. This edect has not been shownin 45 The insertionof impedance in .the

r` elmiszsiv` circuit makes it practical to employ er push pull output circuit as shown inflflgl 6.]

In this connection 'a half wave concentric line 50 'll is provided. The central of the inner conductor includes a blocking capacitor 1 2 which permits diner-ent potentials to be' applied to the' emissiveelectrode II and the anode Il by way tuning the line. The output load may be applied by tapping the line ata suitable impedance point 19. The push pull type of circuit hasftwice' the power output or the voltage i's by 60 ratio \/2/1 where 1 is the voltage for a s'insle output-circuit. f

iA modification'of push pull circuit is shown in Fig. 7. lin-the modification the secondary emissive electrode I5 and the anode il are con v nected to thc-kBsource thrigh'qusrterwave lines Il, I3.' respectivelv. The terminals 'of a half wave line Il aregconnectedto'points onthe quarter wave lines II, Il at which the imi pedances of the several are apprcprltely the inner conductor ofthe half waveline so that different potentials 'may be applied to the electrodes 5 I'I through the quarter wav lines ondary `electron emission.

-' `eect on the device.

l' 8|, 83 without the half waveiine short circuiting the B voltage source, which is not shown. The output may bederived by tapping the half ,wave line. `In the circuits of Figs. 6 and 7 the .potentials oi the deilecting electrodes 'may i be adjusted or varied as described in connection with Fig. l.

Ilils thefinvention, has been described as an ultra high frequency device employing a secondarily emissive electrode. The input voltages'v control the electron stream and hence thesec- 'I'he operating frequency or periodis chosen near the electron transit time which is controlled by means including deilecting' electrodes. ,The electron transit time has `s.' positive or negative reactive"` The reactive effects may f be employed to control the frequency,4 regeneration or response characteristic.- While in the prior art devices the secondary emiss'ive electrode was generally grounded'for radio frequency potentials, animpedance is included in .the emissive electrode circuit of theinstant invention. This impedance may be used to' control tuning or may be included in apush pulloutput circuit. When the device is employed as an oscillator it is preferable to include mutual coupling oi the proper sign betwe'en the input and output circuits.v Such mutual coupling is often present in the ordinary wiring rof the circuits, especially j when the bypassingisinsuillcient.

I claim as my invention:

l. An ultra high frequency vdevice including a thermionictube having an input circuit,` an out-l put circuit. and an electron path: for adjusting the period of said circuits to correspond approximately to 'the transit time required for electrons to travel said path: and means for varying the electron transit time so that` said electrons have a reactive inuence on said. device. 2. An ultra high; frequency device including4 a thermionic tube having an electron source and .a secondary .emissive electrode, 'an input circuit )circuits to correspond approximately to' the 'transit time for electrons to travel said path;

'and means for adjustingsaid pathlenzthso that electrons travelling said adjusted path havea reactive eect on said device.

3. In an ultra hisltfrequency device, the com- ,binatiorp of a thermlonio tube including im input circuit. a source of'electrons connected to said of leads 13 and-l,respectively. The ends of ssjinput circuit. a. secondary `emissive electrode.

Vthe lin'e may include variable capacitors 11 for means for dellecting electrons from said source v onto said emlssive electrode, an anode for co1- lecting electrons emitted .from said electrode. a resonant circuit connected vto said anode, and

means including said deilectlng means for varying the/length of the path travelled by electronsJ from said sourcelto said emissive electrode so that the reactive-influence of'said electrons will vary the frequency characteristic of said resonant clr cuit.

of electrons, a 4secondary emissive electrode, and an anode electrode for; ving electrons from said emissifve electrode: a variable impedance connected to emissive electrode; a

n resonant circuitconnccd to'sai'd anode; means .lz electronsfromsa'idflource onto c;andu iealnsincludingsaiiddciiect-l forvtiryingthctranslv ttlmeofclccan anode electrode for receiving -electrons from' said emissive electrode; an impedance connected to said secondary emissive electrode, a resonant circuit connected-to said anode; means for deiiecting electrons fromsaid source onto said electrode; and means including said deflecting means for varying the transit time ofelectrons travelling from said sourcev to said emissive electrode whereby they have `a reactive influence on said resonant circuit and whereby said impedance controls the response characteristic of said rescriant circuit.

6. In an ultra, high frequency device the combination of a thermionic tube including a cathode, control electrode, deilecting electrode, secondary emissive electrode, and an anode; an input circuit including said cathode and control electrode; a resonant output circuit eiectively connected in push-pull relation between said emissive electrode and said anode; and means including said deiiecting electrode for adjusting the transit time of electrons passing from said cathode to said emissive electrode.

7. In an ultra high frequency device the combination of a thermionic tube including a cathode, control electrode. detlecting electrode,sec ondary emissive electrode, and an anode; an input circuit including said cathode and control electrode; a pair of quarter wave lines connected respectively to saidemissive electrode and to said anode; a hall!- wave line having its terminals respectively connected to said quarter wave lines: and means including said deecting electrodes for influencing reactively the currents in said lines. l

-5 8. The method of controlling the frequency response characteristic of an ultra high frequency device including a thermionic tube having an electron source, an input circuit connected to said source, and an output circuit which includes the l0 steps of emitting electrons. directing said electrons to said output circuit.| adjusting the periods of said circuits so that they. are of the order of the time required for said electrons to travel from said source to said output circuit, and 15 altering said electron travel time so that said electrons havea reactive influence on the-fre- I quency response characteristic of said device.

9.. The methodof'varying the frequency characteristic of an ultra high frequency device in- 20 cluding an input circuit, an oscillatory output circuit, a cathode. a secondary emissive electrode, a. defiecting electrode and an anode, which includes the steps of emitting electrons from said cathode, deflecting said electrons on said emissive 25 electrode, collecting on Vsaid anode secondary electrons emitted by said emissive electrode.,

applying to said oscillatory circuit the currents corresponding to said collected electrons, ad-

justing the periods of both of said circuits te 

